Device comprising a heat sink and a power module
Patent Information
- Application Number
- EP2024799546
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-11-03
- Filing Date
- 2024-10-30
- Publication Date
- 2026-09-09
AI Technical Summary
Existing power modules in hybrid and electric vehicles face challenges in efficiently dissipating high loss heat output due to high electrical currents and switching losses, which requires effective thermal management to prevent overheating.
A device comprising a heat sink with a heat sideline and a power module with an arched module underside, where a spotted layer and a coating are arranged between the power module and the heat sink, allowing for a soldering connection that compensates for the bending of the module underside and ensures a uniform heat transfer.
The solution provides a significantly improved thermal connection between the power module and the heat sink, enabling efficient and even cooling of the power module, thereby minimizing thermal resistance and preventing overheating.
Smart Images
Figure EP2024080709_08052025_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] title
[0003] Device comprising a heat sink and a power module
[0004] State of the art
[0005] The invention relates to a device comprising a heat sink and a power module having the features of the preamble of independent claim 1.
[0006] Power modules, such as inverter structures or converter structures, are used in hybrid or electric vehicles. For example, inverters are used to operate an electric machine, providing phase currents for the electric machine. The power modules can, for example, comprise a carrier substrate with conductor tracks on which, for example, power semiconductors are arranged, which together with the carrier substrate form an electronic unit. The carrier substrate can, for example, be an AMB (Active Metal Brazed) power substrate or a DBG (Direct Bonded Copper) power substrate. Power semiconductors in power electronics carry high electrical currents. Together with switching losses, the resulting conduction losses cause high heat losses, which must be dissipated in a small area using a cooling concept.The maximum permissible semiconductor temperature is critical to failure, which is why minimizing the thermal resistance between the power module and the heat sink is of key importance. During operation, the power module generates heat that must be dissipated to a heat sink. For this purpose, the electronics unit is thermally connected to the heat sink. The heat sink is made of aluminum, AlSiC, or copper alloys, for example. Pins or fins can be arranged inside the heat sink to increase the heat-transfer surface and intensify heat transfer. To achieve low thermal resistance between the carrier substrate of the power module and the heat sink, the carrier substrate is bonded to the heat sink using a soft soldering or sintering process. For this purpose, the top surface of the heat sink can be coated with a material suitable for a soft soldering or sintering process.
[0007] Disclosure of the invention
[0008] According to the invention, a device comprising a heat sink with a heat sink upper side and a power module with a module lower side is proposed. The power module is fastened to the heat sink, wherein the module lower side faces the heat sink upper side. A solder layer and a coating are arranged between the power module and the heat sink, wherein a coating lower side of the coating is materially connected to the heat sink upper side, wherein a solder lower side of the solder layer is materially connected to a coating upper side of the coating, and a solder upper side of the solder layer is materially connected to the module lower side. According to the invention, the module lower side of the power module is curved inwards, and the coating upper side of the coating has a raised portion.
[0009] Advantages of the invention
[0010] Compared to the prior art, the device with the features of the independent claim has the advantage of enabling particularly good thermal connection between the power module and the heat sink. The power module is cooled particularly efficiently and evenly. Due to the temperatures during soft soldering (approx. 200-250°C), the different materials with different thermal expansion coefficients cause bending of the module's underside, for example, the power module's carrier substrate. For example, the power module has a bulbous shape. This can lead to an inhomogeneous thickness of the solder layer, as the solder fills the gap between the coating and the power module and then solidifies. Since the solder layer, e.g., formed as a soft solder layer, has poor thermal conductivity, the thickness of the solder layer is sometimes crucial for effective cooling of the power module.Due to the typical bending of the power module and the semiconductor switches typically located in the center of the power module, a thickened solder layer in this area is particularly detrimental to cooling. By raising the top surface of the coating, the distance between the top surface of the coating and the bottom surface of the module is advantageously reduced. The top surface of the coating can be curved or stepped. Thus, for example, the coating is higher in the center of the power module than at the edges of the power module. This compensates for the bending of the bottom surface of the power module, and the solder layer thickness remains largely homogeneous or can even be thinner in the center of the power module than at the edges.
[0011] Further advantageous embodiments and developments of the invention are made possible by the features specified in the subclaims.
[0012] According to an advantageous embodiment, the curvature in the module underside extends over the entire module underside. This can be particularly the case for modules in which the power semiconductors are arranged in the center of the module.
[0013] According to an advantageous embodiment, the coating's upper surface is curved. The shape of the coating's upper surface is thus adapted to the shape of the module's underside. This ensures advantageously uniform and efficient heat dissipation from the power module to the heat sink.
[0014] According to an advantageous embodiment, the curvature in the coating's upper surface extends across the entire module's underside. This ensures a thin solder layer across the entire module. This allows heat from the power module to be effectively and efficiently dissipated to the heat sink.
[0015] According to an advantageous embodiment, the solder layer between the coating top surface and the module bottom surface has a uniform solder thickness. The curvature of the coating top surface is complementary to the module bottom surface. This creates a gap of uniform width between the coating top surface and the module bottom surface. The gap is filled by the solder layer.
[0016] According to an advantageous embodiment, the coating upper side is curved and the heat sink upper side is flat. This allows a simple heat sink with a flat cooler upper side to be used without the cooler upper side having to be reworked. The curvature in the coating surface can then be easily created when applying the coating to the cooler upper side. The coating then has an inhomogeneous thickness. This compensates for the differences in distance between the heat sink and the curved module underside, allowing a uniform and thin solder layer to connect the module to the heat sink. In contrast to the solder layer, the coating can be made of a material with good thermal conductivity, such as copper. This means that despite the inhomogeneous thickness of the coating, heat is dissipated well and evenly from the module to the heat sink.
[0017] According to an advantageous embodiment, the heat sink top surface is curved. This allows the cooler itself to be adapted to the curvature of the module's underside. The coating can then be easily applied to the curved cooler top surface in a uniform thickness. The coating is then curved and has a curved coating top surface.
[0018] According to an advantageous embodiment, the coating between the solder underside and the heat sink top side has a homogeneous coating thickness. Such a coating can advantageously be easily applied to the heat sink using a variety of standard coating methods.
[0019] According to an advantageous embodiment, a cooling channel is formed in the heat sink, which runs from an inlet opening of the heat sink to an outlet opening of the heat sink and through which a cooling medium can flow. A turbulence structure is arranged in the cooling channel. The turbulence structure is arranged, for example, directly below the power module. The heat from the power module can thus be well and efficiently conducted to the heat sink and dissipated by the cooling medium flowing through the heat sink.
[0020] According to an advantageous embodiment, the heat sink comprises at least one base plate and at least one cover plate, wherein the cooling top side is formed on the cover plate, wherein the base plate, in particular as a deep-drawn sheet, is formed with a recess, wherein the cover plate covers the recess in the base plate, so that the cooling channel is formed in the recess of the base plate between the base plate and the cover plate. On such a heat sink, the cover plate can advantageously be easily machined, so that the curvature on the module underside can be compensated for by the shape of the heat sink top side and / or the coating top side.
[0021] Short description of the drawings
[0022] Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description.
[0023] Fig. 1 shows a cross section through a schematic representation of a first embodiment of a device,
[0024] Fig. 2 shows a cross-section through the schematic representation of a second embodiment of the device. Embodiments of the invention
[0025] Fig. 1 and Fig. 2 show the device 1 in which a power module 40 is connected to a heat sink 10.
[0026] The power module 40 comprises, for example, power circuits. These can be power circuits, such as inverter structures or converter structures, of hybrid vehicles or electric vehicles. The power module 40 comprises a carrier substrate with conductor tracks, on which, for example, power semiconductors are arranged, which together with the carrier substrate form an electronic unit. The carrier substrate can be, for example, an AMB (Active Metal Brazed) power substrate or a DBG (Direct Bonded Copper) power substrate. The power module 40 has a module bottom 42. The module bottom 42 of the power module 40 can, for example, be an underside of the carrier substrate. The module bottom 42 of the power module 40 is made of copper, for example. The module bottom 42 of the power module 40 is curved inward. The curvature in the module bottom 42 extends over the entire module bottom 42.The module bottom 42 is concave.
[0027] During operation, the power module 40 generates heat, which is dissipated to the heat sink 10. For this purpose, a module underside 42 of the power module is arranged on a cooler surface 11 of the heat sink 10. The heat sink 10 can be made of aluminum, AlSiC, or copper alloys, for example. As in the exemplary embodiments illustrated in the figures, the heat sink can be formed, for example, on plates stacked one above the other and connected to one another, for example, by soldering. In the exemplary embodiment, the heat sink 10 comprises a base plate 12 and a cover plate 13. The cover plate 13, together with the base plate 12, forms outer walls of the heat sink 10. The base plate 12 forms a bottom side of the heat sink 10. The cover plate 13 forms a top side of the heat sink 10.The base plate 12 and / or the cover plate 13 can be formed, for example, from a material with high thermal conductivity, for example, from a metal, such as aluminum. The base plate 12 and / or the cover plate 13 can be sheet metal, for example. The base plate 12 and / or the cover plate 13 each have a constant thickness d, for example. The base plate 12 and the cover plate 13 can, for example, have the same thickness or different thicknesses.
[0028] The base plate 12 is designed, for example, as a deep-drawn part. One or more recesses are formed in the base plate 12. The base plate 12 is essentially trough-shaped. The cover plate 13 is arranged on the base plate 12 such that the recess in the base plate 12 is covered by the cover plate 13. The base plate 12 and the cover plate 13 are arranged on one another such that the recess forms a space in which a cooling channel 15 runs. An edge of the base plate 12, which is formed, for example, in a plane, is at least partially connected to an edge of the cover plate 13. The base plate 12 and the cover plate 13, or, for example, other plates, abut one another, for example, at their edges and are connected to one another. This creates a closed space in which the cooling channel 15 runs. For example, an edge of the base plate 12 surrounds the recess in the base plate 12.The edge of the base plate 12 rests, for example, directly or with the interposition of one or more intermediate plates or intermediate layers, on an edge of the cover plate 13. The edge of the base plate 12 is firmly connected, in particular soldered, to the edge of the cover plate 13. The base plate 12 and the cover plate 12 can be connected to each other, for example, by means of a brazing process.
[0029] Furthermore, the heat sink 10 comprises an inlet opening (not shown in the figures), through which a cooling medium can be supplied to the cooling channel 15 in the heat sink 10. Furthermore, the heat sink 15 comprises an outlet opening (not shown in the figures), through which the cooling medium can flow out of the cooling channel 15 and the heat sink 10. The cooling medium can be water, for example. The inlet opening and / or the outlet opening can be formed, for example, by openings in the base plate 12 and / or cover plate 13. A cooling medium flow can flow through the cooling channel 15 from the inlet opening to the outlet opening. A turbulence structure 16 is arranged in the cooling channel 15. The turbulence structure 16 is used to increase and specifically control a heat transfer coefficient of the heat absorbed by the heat sink 10 to the cooling medium.The turbulence structure 16 is formed in the cooling channel 15, for example, in the form of pins or ribs. The turbulence structure 16 generates a high pressure loss of the cooling medium in the cooling channel 15. In this exemplary embodiment, the turbulence structure 16 is designed as a turbulence insert that is inserted into the cooling channel 15 of the heat sink 10. The turbulence structure 16 is arranged between the cover plate 13 and the base plate 12. The turbulence structure 16 can extend from the cover plate 13 to the base plate 12 completely through the cooling channel 15. In particular, the turbulence structure 16 is in indirect and / or direct heat-conducting contact with the base plate 12 and with the cover plate 13. The turbulence structure 16 is attached to the cover plate 13 and / or the base plate 12, for example, by means of a brazing process. When flowing through the turbulence structure 16, the cooling medium is locally swirled.The turbulence structure 16 has a surface-enlarging, flow-guiding, and heat-transferring structure. The turbulence structure 16 is formed, for example, from a metal with good heat conduction, such as aluminum. In the exemplary embodiments illustrated here, the turbulence structure 16 is formed as a structured sheet metal. The turbulence structure 16 comprises, for example, a plurality of turbulence sections, which are arranged at an angle to the flow direction of the cooling medium through the cooling channel 15 in order to turbulently swirl the cooling medium flowing through the cooling channel 15. This allows heat to be dissipated particularly effectively. The heat sink 10 has a heat sink top side 11. In this exemplary embodiment, the heat sink top side 11 is the surface of the cover plate 13 facing the power module 40. The cover plate 13 is formed in one piece.The cover plate 13 is made entirely of the same material, for example, aluminum. The heat sink top 11 faces the module bottom 42.
[0030] A coating 20 is arranged on the heat sink top side 11. The coating 20 is, for example, formed in one piece. The coating 20 is made continuously from the same material. The coating 20 is, for example, made of copper or nickel. The coating 20 is, for example, materially bonded to the heat sink 10, in particular over the entire planar extent of the coating 20. A coating underside 22 adheres materially, in particular directly, to the cooler top side 11 of the heat sink 10. The coating 20 can, for example, be applied to the cooler top side 11 using a cold gas spraying process. The coating 20 has a coating top side 21 facing away from the coating underside 22. The coating top side 21 faces the module underside 42. The coating top side 21 of the coating 20 has a raised portion 25.In the illustrated embodiments, the coating upper side 21 is curved. The curvature extends over the entire module underside 42. The coating upper side 21 is curved towards the power module 42. The curvature in the coating upper side 21 is complementary to the curvature in the module underside 42. For example, the coating upper side 21 can run parallel to the module underside 42. The coating upper side 21 has, at least in sections, the same curvature as the module underside 42. The optimal shape of the coating upper side 21 is matched to the module underside 42. The height difference in the coating 20 between the minimum and maximum is in particular between 100 μm and 200 μm, but can also be lower or higher.
[0031] The module underside 42 of the power module 40 is soldered onto the coating 20 on the heat sink 10. Thus, a solder layer 30 is arranged between the power module 40 and the coating. The solder layer 30 is, for example, a soft solder layer. The solder layer 30 is formed in one piece. The solder layer 30 is continuously formed from the same material. The solder layer 30 is integrally connected to the coating 20 on the heat sink 10 and to the module underside 42 of the power module 40. The solder layer 20 has a solder underside 32 and a solder top side 31. The solder top side 31 faces away from the solder underside 32. The solder underside 32 of the solder layer 30 is integrally connected, in particular directly, to the coating top side 21 of the coating 20. The solder top side 31 of the solder layer 30 is firmly bonded to the module bottom side 42. The solder layer 30 is arranged between the coating top side 21 and the module bottom side 42.The curved coating upper side 21 creates a uniform solder layer 30. The solder layer 30 has, in particular, a constant solder thickness Id over the flat extent of the solder layer 30. The solder thickness Id is measured perpendicular to the module underside 42. The solder layer 30 is domed. Fig. 1 shows a first exemplary embodiment of the device 1. In the first exemplary embodiment, the coating upper side 21 is curved and the coating underside 22 is flat. Thus, the coating 20 in this exemplary embodiment does not have a constant thickness bd. In this exemplary embodiment, the coating 20 has a greater coating thickness bd in the middle than at the edges of the coating 20. The coating thickness bd is measured perpendicular to the cooler upper side 11. In the exemplary embodiment shown in Fig. 1, the cooler upper side 11 is also flat.The coating thickness bd can be flexibly adjusted in height, for example, using a cold gas spraying process.
[0032] Fig. 2 shows a second embodiment of the device 1. In this embodiment, the heat sink top side 31 is curved. The heat sink top side 31 is higher in the middle than at the edges. The heat sink top side 31 is curved away from the heat sink 10. The curvature of the heat sink top side 31 extends over the entire module bottom side 42. The heat sink top side 31 can be bent in a process downstream of the manufacture of the heat sink 10. However, the tolerances of the individual parts of the heat sink 10 can also be coordinated such that after the brazing process, in which the individual parts are soldered together, the heat sink top side is curved. For example, machining of the heat sink 10 is also possible.The coating 20 between the solder underside 32 and the heat sink top side 11 has a constant coating thickness bd, particularly across the surface extent of the coating. The coating thickness bd is measured perpendicular to the cooler top side 11.
[0033] Of course, further embodiments and mixed forms of the embodiments shown are possible.
Claims
Claims 1. Device comprising a heat sink (10) with a heat sink top side (11) and a power module (40) with a module bottom side (42), wherein the power module (40) is fastened to the heat sink (10), wherein the module bottom side (42) faces the heat sink top side (11), wherein a solder layer (30) and a coating (20) are arranged between the power module (40) and the heat sink (10), wherein a coating bottom side (22) of the coating (20) is integrally connected to the heat sink top side (11), wherein a solder bottom side (32) of the solder layer (30) is integrally connected to a coating top side (21) of the coating (20) and a solder top side (31) of the solder layer (30) is integrally connected to the module bottom side (42), characterized in that the module bottom side (42) of the power module (40) is inwardly is curved and the coating top side (21) of the coating (20) has an elevation (25).
2. Device according to claim 1, characterized in that the curvature in the module underside (42) extends over the entire module underside (42).
3. Device according to one of the preceding claims, characterized in that the coating upper side (21) is curved.
4. Device according to one of claims 3, characterized in that the curvature in the coating upper side (21) extends over the entire module underside (42).
5. Device according to one of claims 3 to 4, characterized in that the solder layer (30) between the coating top side (21) and the module bottom side (42) has a homogeneous solder thickness (Id).
6. Device according to one of the preceding claims, characterized in that the coating upper side (21) is curved and the heat sink upper side (11) is flat.
7. Device according to one of claims 1 to 5, characterized in that the heat sink upper side (31) is curved.
8. Device according to claim 7, characterized in that the coating (20) between the solder underside (32) and the heat sink top side (11) has a homogeneous coating thickness (bd).
9. Device according to one of the preceding claims, characterized in that a cooling channel (15) is formed in the cooling body (10), which runs from an inlet opening of the cooling body (10) to an outlet opening of the cooling body (10) through the cooling body (10) and through which a cooling medium can flow, wherein a turbulence structure (16) is arranged in the cooling channel (15).
10. Device according to claim 9, characterized in that the cooling body (10) comprises at least one base plate (12) and at least one cover plate (13), wherein the cooling top side (11) is formed on the cover plate (13), wherein the base plate (12), in particular as a deep-drawn sheet, is formed with a recess, wherein the cover plate (13) covers the recess in the base plate (12), so that the cooling channel (15) is formed in the recess of the base plate (12) between the base plate (12) and the cover plate (13).